Field of the Invention
The present invention relates to a signal processing apparatus.
Priority is claimed on Japanese Patent Application No. 2013-223891, filed Oct. 29, 2013, the contents of which are incorporated herein by reference.
Description of Related Art
A process control system provided in a plant or a factory or the like generally includes on-site devices called field devices (measuring devices, and actuators), a controller controlling the field devices, and a host device managing or controlling the field devices and the controller. The field devices, the controller, and the host device are in connection with one another via a communication means. In such a process control system, the collector is for collecting process values (for example, measured values of the pressure, the temperature, and the flow rate) obtained by the field devices, and controlling the field devices based on the collected process values under the control of the host device.
A system for measuring and recording physical quantity (for example, a pressure, a temperature, a flow rate, and optical power) includes a sensor for detecting the physical quantity, and a signal processing apparatus (for example, power meters, and recorders) connected to the sensor. In such a system, the signal processing apparatus is for collecting signals detected by the sensor, and performing a pre-determined processing (for example, a measuring processing, and a recording processing).
Japanese Patent No. 3430287 discloses a modular measuring device connected to a personal computer and capable of performing a measurement under the control of the personal computer. The modular measuring device includes a memory for recording information of the type of module or the like. The personal computer is for reading the information of the type of module recorded in the memory of the module to recognize the type of module.
There are various types of field devices, which are used for the above-stated process control system, depending on its measuring targets and its operation targets. The forms of the signals input to and output from the field device are variable. There are some cases where various types of field devices supplied from various vendors are used in the above-stated process control system. Therefore, it is often the case that a signal processing apparatus (specifically, a signal processing apparatus including an interface module and an I/O module) for performing a signal processing enabling various field devices to be connected to the controller is provided between the field device and the controller in the above-stated process control system. In the above-stated system for measuring and recording physical quantity, the more the types of and the number of the connected sensors increase, the more modules including similar functions to those of the interface module are used.
The more the types of the connected field devices increase, the more the number of the interface modules increases. The interface modules including functions depending on the signal form of the connected field device are used. For example, if it is necessary to convert signals output from the field device, the interface module including a function of converting signals is used. Therefore, since, as with the case of the field devices, the various types of the interface modules are used, it is necessary to identify the type of the interface module by the controller, for example, in order to facilitate maintenance in case of trouble.
The following methods (1) to (3) are considered as a method for identifying an interface module.
(1) A method of providing a memory disclosed in Japanese Patent No. 3430287 to the interface module
(2) A method of providing a CPU (central processing unit) to the interface module
(3) A method of providing a port for outputting a plurality of bits of signals to the interface module
In the method (1), identification information stored in the memory is read to identify the type of the interface module. In the method (2), the communication with CPU is performed to identify the type of the interface module. In the method (3), for example, a plurality of pull-up resistors or pull-down resistors, each of which specifies the level of bit string output from the port, is provided and the bit string output from the port is referred to identify the type of the interface module.
In the methods (1) to (3), there are some cases where the cost is increased, or the number of the wirings connected to the interface module is increased. In the methods (1) and (2), it is thought that it is possible to perform notification of a problem in the interface module (for example, a misalignment of wiring connected to a field device). However, in the method (3), there are some cases where notification of the problem cannot be performed.